From NCERT NEET - 2018
Ans: 4. Francois Jacob and Jacques Monod – Lac operon
👉Prions : In modern medicine certain infectious neurological diseases
were found to be transmitted by an agent consisting of abnormally folded
protein. The agent was similar in size to viruses. These agents were called
prions. The most notable diseases caused by prions are bovine spongiform
encephalopathy (BSE) commonly called mad cow disease in cattle and
its analogous variant Cr–Jacob disease (CJD) in humans.
👉The Lac operon
The elucidation of the lac operon was also a result of a close association
between a geneticist, Francois Jacob and a biochemist, Jacque Monod. They
were the first to elucidate a transcriptionally regulated system. In lac operon
(here lac refers to lactose), a polycistronic structural gene is regulated by a
common promoter and regulatory genes. Such arrangement is very common
in bacteria and is referred to as operon. To name few such examples, lac
operon, trp operon, ara operon, his operon, val operon, etc.
